They are pretty small tubes Bob, sometimes you can find a pack of very small bottle brushes, but even these are large compared with the size of the tubes. Possibly some “Pipe Cleaners” purchased from a tobacconist might do the job, or some very thin Wooden dowelling, or maybe some piano wire or similar, but be gentle when using it. Usually the deposits found are soft and slushy, but there might be some barnacle shell within the tubes, and in which case you can usually remove the tube nest, and then soak it in vinegar which will help to dissolve the shells left by any temporary squatters. Take care when putting the tube nest back in place to locate it in the same position.
